Geographic Information System-Based Source Estimation of Copper Pollution in Lake Itezhi-tezhi and Metal-Accumulation Profiles in Oreochromis spp. from Both Field and Laboratory Studies

摘要

The Copperbelt region, upstream of the Kafue River, including Lake Itezhi-tezhi (ITT), in Zambia has extensive copper (Cu) mines. In our field study, geographic information system (GIS) analysis in lake sediment indicated that the northern part of the lake, Copperbelt region, could be the Cu pollution source. Concentrations of Cu in stomach contents between fish species were not significantly different. However, Oreochromis spp. liver showed significantly higher Cu concentrations than those in other fish species. Log liver [Cu], standard length, and nitrogen stable isotope ratio were positively correlated only in Oreochromis spp. In the laboratory study, O. niloticus and Oryzias latipes were exposed to Cu for four days and recovery phases up to 28 days were examined. O. niloticus showed significantly higher concentrations of Cu compared with O. latipes at all sampling points. Significantly higher concentrations of Hg in Schilbe intermedius liver than for other fish species were observed, while Oreochromis macrochir showed significantly higher concentration of Cd. In conclusion, the northern part of the lake could be the source of Cu pollution in Lake ITT. Diet may not be the reason for high Cu accumulation in Oreochromis spp. Results from both field and laboratory studies imply that Oreochromis spp. contain high concentrations of Cu under normal physiological conditions.